What is nanotechnology? Although responses may vary per individual, my bottom line is that it is the technology for the ultimate utilization of materials. New nanomaterials are being developed every day. In order to extract the functionality of these to the utmost and allow them to demonstrate their individual characteristics 100%, we need a technology to place the required quantity of nanomaterial in the required position. This was my conclusion.

The silicon technology which sustains present-day electronics is a technical system of high versatility, with exposure and etching technologies at its core. Meanwhile, for the patterning of nanomaterials, these conventional technologies are not necessarily the best answer. The positioning of nanomaterials is synonymous with the positioning of functionality. Functionality is imparted not through conventional processing such as cutting, carving or shaving, but through new methods such as painting, adding on, or application of materials.

To do this, a technology that could arrange microscopic quantities with precision was required. Since little or no such technology existed at the time, I was forced to make it myself. This was my start. In other words, it was a completely personal need-oriented research.

At first, I had the simple notion that if we used a small nozzle and applied a large pressure, the fluid would shoot out. However, it was actually not that simple. Figure 1 shows the relationship between kinetic energy of a water droplet and surface energy. The common velocity of 5 m/s for an inkjet droplet is used for the kinetic energy. In order for the droplet to shoot out, it must overcome surface tension. Surface energy is proportional to the square of the droplet diameter and kinetic energy is proportional to the cube of the diameter. With microscopic droplets, the surface energy becomes larger than kinetic energy. Thus it becomes difficult to impart sufficient kinetic energy to the discharge fluid or the droplets shooting out. As a result of various efforts of trial and error, I was able to achieve the prototype of the current super-fine inkjet. My research during this time was rather closer to Type 1 Basic Research than application research.

I presented the achievements of my basic research described above at the International Nanotechnology Exhibition & Conference (nanotech 2002). I received a significant response at the time, including many requests to make the device commercially available. However, the actual device itself was something a researcher developed as his own research tool and did not necessarily match general needs. Therefore, I redefined my goals to incorporate the needs of society. Regarding this endeavor, we are still in the middle of technical development, thus we may not yet be considered completely clear of the Valley of Death.

Research during this period consisted of the task of redefining my research goals by incorporating the needs of society - rather than the needs and seeds of myself, the researcher, accumulating the usable technology, and also adding or developing any missing areas. Although the work was fragmentary, I made progress by combining various technical elements. I received the help of countless individuals inside and outside of AIST as I encountered many aspects which I could not resolve on my own.

There were many unexpected surprises during the course of my research. One was the high drying characteristics of the microscopic droplet. Normally, fluid that lands on a substrate changes shape so as to minimize surface energy. The effect of surface tension becomes more prominent as the droplet becomes more minute, thus patterning exactly as planned is not easy. Conventionally, the problem of how to prevent the occurrence knobby distortions called bulges was important in the development of inkjet technology, and constituted the know-how owned by manufacturers. In case of my inkjet, the droplet size is so small that it dries immediately upon landing. The volume of fluid is limited, and thus bulges do not easily form. Further, actively exploiting this drying characteristic, the three-dimensional forms such as shown in Figure 2 can be built by the inkjet. Formerly, in order to create such microscopic three-dimensional forms, a vacuum process or expensive equipment was necessary, but by using the super-fine inkjet, a three-dimensional structure can even be added on afterwards, in the atmosphere at room temperature, on a target spot on the substrate. The super-inkjet equipment is so compact that it can be placed on a desk, as shown in Figure 3. This is a unique characteristic not seen in other technologies.

The other surprise for me was that such a hand-made piece of equipment could perform with fair precision. Today’s cutting edge equipments for manufacturing industrial products are all large and expensive. The reason is that they need to guarantee accuracy for combining things built using various machines. However, if incorporation of the necessary functions were possible on one processing table, it would be possible to make the equipment simpler.

Presently, based upon this new viewpoint obtained during the course of research, I am considering starting an endeavor going back once again to Type 1 Basic Research. By adding the essentials I learned from Type 2 Basic Research, I hope to make my second round of Type 1 Basic Research something different.

The inkjet technology is a technology for placing the required quantity of material in the required position. Not limited to inkjets, I believe that the method of making things will be reassessed in the future, from cutting, carving and shaving, to painting, adding on and applying. This applies to printable electronics, rapid prototypes, and may even include the technology referred to as near net shape. Instead of using materials loosely as bulk, we can draw out their functionality to the maximum. Expensive equipment and clean rooms may thus become unnecessary, as we conduct resource- and energy-saving production low in environmental load using equipment of a size only several times that of the product.

In the far future, we may see an SF-like world, in which an industrial plant is able to produce various objects based upon data, so hardware design data fly about the Internet and software and hardware are evolved simultaneously.